The design of aeronautical structures requires an assurance that the created designs fulfil the guidelines established by aerodynamics without compromising the functionality of the parts and the aesthetics of the exterior elements. All these premises must be met at the same time, and in turn it is advisable to optimize the times and costs of manufacturing the aeronautical structures.
The trailing edge zone of the elevator of an aircraft's horizontal stabilizers manufactured of a composite material, and in particular carbon fibre, currently presents a drop-off or change of gradient zone in the connection of the claddings made of carbon fibre to the connecting clip type elements, typically made of a metal material, so that the elevator is protected against lightning impacts.
Thus, the drop-off or change of gradient presented in particular by the claddings of the elevators of the horizontal stabilizer surfaces may, on occasions and due to the difficulty of the geometry, develop wrinkles in the carbon fibre and air pockets, which leads to a subsequent delamination of these zones. These delaminations require laborious processes of repair that, in the most favourable case, involve a minimum of 5 hours of work, as the application of new cycles of autoclave curing of the surface in question is required. On the other hand, the machine time that is required to tape off this zone, and which requires close monitoring and constant control during the process, must also be taken into account.
This drop-off or change of gradient in the connection thus poses a fundamental problem, which is the lack of aerodynamic continuity of the surface. Attempts have been made to solve this problem in different known ways.
One of these solutions consists of using an aerodynamic fill material in the connection zone of the claddings to the connecting clip type elements, so that this fill will make these connecting clip type elements of the claddings flush with the claddings themselves, thus achieving an improved outer appearance or quality of the surface and improving its continuity, and at the same time achieving a better aerodynamic performance of this surface. The problem with this aerodynamic fill material is that it is subject to cracking during its in-service life on the aircraft, which also causes the corresponding cracking and subsequent flaking of the external surface paint, with the resulting complaints of the customers receiving the aircraft because the surface has a highly deteriorated appearance.
Another known solution is to fill the zone to be treated, i.e. the edges of the connecting clip elements where they connect to the claddings, by means of a sealant material strip. This solution does not maintain the continuity between the connecting clips and the claddings, and thus the visual appearance of the outer surface is not as good. Moreover, there is an aerodynamic penalty to this solution, which translates into increased parasitic resistance of the aircraft.
Therefore, there is a need to solve the problem of the above mentioned surfaces, in terms of their quality and also in terms of their assembly and the actual process of manufacturing them.
This invention is proposed to solve the problems described above.